TH-18 Flat to 35hz! (Xoc1's design) - Page 167 - diyAudio
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Old 5th June 2014, 06:24 PM   #1661
GM is online now GM  United States
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From just calculating it and due to having both a sub and woofer at some separation with the mic biased a little high, I'm thinking both the ~180? and ~220? Hz notches are floor bounce.

GM
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Old 5th June 2014, 09:13 PM   #1662
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Thank you all for your comments and suggestions.

I will make new measurements separately for each driver.

The XO is with 24db so is that common that you need to reverse the leads on the tweeter? I know that its common for 12db.

I will also try to adjust the hight og the mic.

If I should dial in a delay, it would be calculating the distance between both drivers voice coils?

There is a 6.2ms delay on the whole top to allign with the sub.

Best, Andy
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Old 9th June 2014, 03:38 AM   #1663
RNMarsh is offline RNMarsh  United States
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How about THD vs Frq -- How clean are they!?


THx-RNMarsh
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Old 10th June 2014, 07:47 AM   #1664
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Default second round measurments

I was able to do some more measuring and wanted to share.

The setup is the same as before, but levels have changed, since I don't have a SPL meter.

REW with a DBX RTA mic and a not validated calibration file I found with google. External calibrated Yamaha Steinberg soundcard, DBX DRPA+ setup with LOW: HP 30hz/24db, MID: HP 100hz/12db, LP 1.12khz/24db HIGH: HP 1.4khz/24db. MID and HIGH has a 6.2ms delay to allign with the sub. The mic is 4meters from the speaker and 1.6 meters high, pointing directly to the horn.

Before:

cad152_th18_before_reversing_horn_2.88v_4meters.jpg

After:

cad152_horn_reversed_-7db_th18.jpg

In the after I reversed the leads on the horn, which I think helped removing quite a few dips in the mid area.

These are only frequency measurements, so no THD, Phase etc. so far.

I did actually made an attempt to make SPL measurements with the XTA mic, John Reekie method of making SPL measurements without SLM but I am not able to read and verify the results.

The measurement below ended up being a 10volt measurement, I think because I made some initial SPL calibration settings with a headroom first being to small for a 2.83v input(clipping) and then making a headroom to big(+20db), which called for the high output?

The mic is 4 meters from the sub and 1.6 meters above ground and the 10 volts is measured by plugging in an extra speaker cable in the bag of the sub(parallel) and attach a Voltmeter at the end of that cable.

cad152_th18_10v_4meters.jpg

Input is very welcome.

I am planning on doing more measurments i.e. I want to make sure that the metal grill, which has 47% airflow has no negative impact. And later excursion vs. Cone correction testing etc.

Let me know if you have ideas, also on good maesurement practice.

Best, Andy
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Old 10th June 2014, 10:28 AM   #1665
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Andy,
Your second round measurement looks very good - nice job. The 150 Hz dip looks to deep and sharp to be a floor bounce cancellation. It is probably too narrow to be noticeable but again I was hoping to see traces from each individual driver to debug this. You said that you have not made HD measurements but you have. In REW all measurements automatically generate HD data - just click on HD tab at the top and select harmonics of interest. It is helpful to see first 5 harmonics.
Thanks for sharing. It must sound quite good as it is.
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Old 10th June 2014, 11:32 AM   #1666
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xrk971,

Correction: The LowMid XO is 12db both flanks and not 24db HP.

Thank you for comments and info.
I have the separate measurements for LowMid and Horn:

LowMid: (HP100hz/12db and LP 1.12Khz/12 db)

cad152_lowmid.jpg

Horn: (HP 1.4Khz/24db -7db)

cad152_horn_2meters_1.6meters.jpg

Old measurement of TH-18 Sub:

th18_3.jpg

Can't seem to find the HD tab as you mention. I am using REW ver.5 buil 2142.

/ Andy
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Old 10th June 2014, 10:58 PM   #1667
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Quote:
Originally Posted by Andy1967 View Post
After:

Attachment 423112

In the after I reversed the leads on the horn, which I think helped removing quite a few dips in the mid area.
What LP filter are you using on the TH?
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Old 10th June 2014, 11:50 PM   #1668
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Quote:
Originally Posted by Brian Steele View Post
What LP filter are you using on the TH?
Brian,

In post 1664 Andy writes the HP is 30 Hz 24 dB, unspecified filter (BW would have almost no affect on response at 30 Hz, LR would have a little ) but the measured response rolls off below 45 Hz, around 10 Hz higher than the few Xoc1-TH18s measurements seen previously.

Art
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Old 10th June 2014, 11:58 PM   #1669
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Quote:
Originally Posted by weltersys View Post
Brian,

In post 1664 Andy writes the HP is 30 Hz 24 dB, unspecified filter (BW would have almost no affect on response at 30 Hz, LR would have a little ) but the measured response rolls off below 45 Hz, around 10 Hz higher than the few Xoc1-TH18s measurements seen previously.

Art
That's the HP filter. I was asking about the LP filter. I'm assuming that he's not running it full range above that 30 Hz HP filter.
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Old 10th June 2014, 11:59 PM   #1670
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Andy1967 are you using the 18SW100 woofer or another?
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